Homologous recombination using targeting vectors that are specifically designed to add, delete, or replace a particular nucleic acid sequence at a genomic locus is a popular approach to achieving a desired genomic modification in a cell. A nuclease that is specifically engineered to introduce a nick or a double-strand break at or near a target locus can be used in combination with a targeting vector to enhance the efficiency of homologous recombination at the target locus.
Although the art of targeted modification through homologous recombination has advanced considerably over the last two decades, difficulties still remain with achieving an acceptable targeting efficiency using targeting vectors. Methods are needed which improve the efficacy and efficiency by which targeted modifications are produced.